1. Field of the Invention
The present invention relates to the technical field of lighting apparatuses, and in particular to the technical field of reflectors for lighting apparatuses.
2. Description of the Related Art
The light emission quality is one of the most important parameters of lighting apparatuses. Reflectors, diffusers and light emission devices are designed and selected so as to obtain precise lighting conditions, in terms of emission diagram and light intensity emitted, as well as in terms of lighting uniformity. The light emission uniformity may be referred to both the illuminance and the chromaticity.
When reference is made to the lighting uniformity in terms of illuminance, it is necessary to determine the differences in the density distribution of the radiated lumens. The less uniform the emission, the more perceivable the irregularities in the light distribution such as spots, or rings or light smears, which interrupt the uniformity of the emitted light field.
On the other hand, when reference is made to the lighting uniformity in terms of chromaticity, it is necessary to determine any variations in the color temperature within the lighted field due to irregularities in the light emission device. Any flaws in the emission uniformity in terms of illuminance may be due, for example, to irregularities in the reflecting surface of the reflector.
Considering the case of roto-symmetric reflectors having, for example, a parabolic or elliptic profile, we have that the reflection of a part of the emission of the light source takes place according to the local inclination of the reflector portion impinged by the incident light rays, in observance of the Euclidean theories according to which the incidence angle is equal to the reflection angle.
Roto-symmetric reflectors are generally manufactured with molding and turning techniques which often produce small irregularities on the reflecting surface, which may cause considerable non-uniformity in the beam of the reflected light emission and thus, in the illuminance produced by the lighting apparatus.
Illuminance non-uniformities may also be caused by asymmetries in the light emission sources which may, for example, be related to the non-symmetric structure of filament and halogen lamps.
Also flaws in the emission uniformity in terms of chromaticity may be due to irregularities or flaws present in the light sources used. If we consider the light sources of the metal iodide or discharge type, for example, we have that the rare earths contained in the light source bulb tend to deposit on the bottom of the same bulb over time. Therefore, if the lighting apparatus is installed so that the bulb is in vertical position and the light bulb socket at the top, the deposition of the rare earths on the bottom of the bulb has no great effect on the overall light emission whereas if the lighting apparatus is installed so that the bulb is not in vertical position, the deposition of rare earths may affect the direct emission towards the reflector, emission that will have a different chromaticity with respect to that not crossing the above deposition of rare earths. The resulting overall effect will be an emission with zones having different color temperatures, with negative consequences on the quality of the lighting provided, especially in the case of lighting of products on display or works of art displayed in museums.
In order to obviate the above-described drawbacks and make the lighting resulting from the reflection more uniform, the reflecting surface of the reflector is divided into a certain number of surface segments having each a curved or arched reflecting surface adapted to distribute the reflected light rays, making them more uniform in the space and carrying out a mixing of the reflected beam which is such as to absorb any non-uniformity in terms of illuminance or chromaticity.
f surface segments provided with curved reflecting surface are used, we have a plurality of diverging reflections so that the single reflected rays occupy the space more uniformly, thanks to a lower light density present on the surface of the single reflecting surface segments.
Intervening on the curvature radius of the surface of these surface segments it is therefore possible to directly act on the uniformity of the light emission of the lighting apparatus.
Several examples of reflectors exist in the prior art, comprising a segmented reflecting surface.
U.S. Pat. No. 6,361,175 relates to a reflector of which the reflecting surface is divided into a plurality of convex surface segments provided with a certain curvature and with a certain position with respect to the optical axis of the reflector so as to generate a resulting lighting profile having a certain shape.
U.S. Pat. No. 4,021,659 relates to a dichroic halogen lamp provided with a reflector, also provided with a reflecting surface divided into a plurality of convex surface segments provided with a curvature adapted to reach a certain mixing level of the reflected light.
Also patent DE69130738 relates to a reflector having the internal reflecting surface divided into multiple convex surface segments provided with curvature radius and arrangement with respect to the optical axis of the reflector.
Finally, patent DE19627940 relates to a reflector in which the surface segments in which the reflecting surface thereof is divided are concave.
In each of the devices object of the above patents, the reflecting surface of the reflector is divided into surface segments provided with one or more curvature radiuses through which the degree and quality of the mixing of the light beam resulting from the reflection are adjusted.
The object of the present invention is to provide a reflector that improves the prior art reflectors providing a mixing degree of the reflected light beam which is higher and more independent of possible surface flaws or of possible flaws and asymmetries of the light emission devices used.